Scissors jack



1957 H. E. HANKEY ETAL 3,

SCISSORS JACK Filed Oct. 23, 1965 FIG! INVENTORS HERBERT EUGENE HANKEY 8 ELMER JAMES HAMRICK BY j/zm m v M ATTORNEYS United States Patent Ohio Filed Oct. 23, 1965, Ser. No. 503,766 2 Claims. (Cl. 254122) This invention relates to jacks of the scissors or lazy tong type, and in particular to a novel trunnion block and drive gear combination for operating the jack.

Lifting jacks embodying the lazy tong principle are common and well known. Most such jacks have a single drive handle adaptor directly connected to a central threaded shaft which operates the linkage mechanism of the jack.

An object of this invention is to provide a gear reduction drive system for the shaft, having a high mechanical advantage for ease of operation.

A further object of the invention is to provide such a drive system, wherein the high advantage drive adaptor is at least as accessible as the main drive adaptor, and is rigidl supported against lateral deflection under improper application of handle pressure.

In accordance with these and other objects which will become apparent hereinafter, the best mode contemplated for the present invention is disclosed in the accompanying drawings wherein:

FIGURE 1 is a side elevational view of a scissors type jack embodying the principles of the improved trunnion and gear reduction drive concept of this invention;

FIGURE 2 is a view taken along the lines 2-2 of FIGURE 1; and

FIGURE 3 is a section of the drive trunnion and gear reduction system substantially as taken along the lines 33 of FIGURE 2.

The drawing illustrates the operative portion of the jack in substantially conventional form, as now well known and widely used. This jack is mounted on a base It! having a large area for seating upon the roadway or other surface below an automobile, for example, and provides a firm support.

A lazy tong system 12 of conventional form provides lift action. A draw trunnion block 14 is pivotally united to upper and lower sets of opposed crossed links in system 12. Trunnion 14 operates in conventional manner, and although not shown in the drawing, has a threaded through opening.

A drive trunnion assembly 16 is connected to the crossed links at the position opposite the draw trunnion 14. The lazy tong system 12 is then connected to a pad 18, located in opposite relation to the base 10. The pad 18 is provided to contact and support a load to be lifted, such as the axle of an automotive vehicle.

A lifting screw 20, having a threaded section 22 making up a substantial portion of its length, and a smooth section 24 near one end, is threadably engaged in the trunniony14. The smooth section 24 is rotatable in trunnion assembly 16, but is fixed against longitudinal movement with respect thereto.

Drive trunnion assembly 16, in the embodiment shown, is constructed on a body portion 26. The lazy tong system 12 is connected pivotally to the body portion 26 by means of a pivot 30 on the side shown in FIGURE 1, and a pivot 31 shown in FIGURE 3. The body portion is held nonrotative with respect to the lazy tong system by these pivots, and drive force from the trunnion assembly 16 is transmitted to the lazy tong system through these pivots.

The lazy tong system 12 is composed of the system of links as shown in FIGURE 1 on one side of the jack, and

an exact duplicate of the links shown in FIGURE 1 are concealed on the opposite side as shown in FIGURE 1. This system, being old and well known, is believed to need no further description. However, it is believed accurate to say that the width dimension of the draw trunnion block 14, and the diameter across the body portion 26 of the assembly 16 has a practical limit in order that the jack will not be excessively bulky in storage and use. Hence, this invention provides a novel advance over the art in that a gear drive system is provided in which a large driving gear attached to the screw 20 is considerably larger than any practical available space between the two lateral sets of linkages. Thus, there is provided a greater gear reduction potential than prior art devices wherein the gear to drive the screw 20 is confined between the lateral confines of the linkage system.

In FIGURE 3, a backing plate 32 is secured to the end of the body portion 26 to provide a rigid extension terminating in an apex area 34. In the context of a jack in an upright position, the apex 34 extends downwardly from the screw 20. An opening 36 in the center of the plate permits the smooth portion 24 of screw 20 to extend through the plate 32. This plate performs the dual function of a protective shield and a rigid mount for a mechanical advantage sprocket system.

A sprocket 38 is secured to the smooth section 24 of screw 26 by means of a pin 40. Because it is secured to the screw, the screw is held against withdrawal through the body portion 26, and therefore as the screw is rotated in a direction to feed through trunnion 14, the screw is placed in tension, and will draw the trunnion 14 and the sprocket 38 toward each other. The sprocket 38 will then be pulled toward the plate 32 and will exert a drive force on the plate which is in turn transmitted therethrough to the body portion 26 and to the pivot pins 30 and 31. Thus, the system 12 is activated to elevate pad 18.

In order to permit relative rotation of the sprocket 38 with respect to the backing plate 32, a thrust bearing 42 is interposed between these two members. The sprocket 38 may therefore drive the screw 20, or if the screw 20 is directly driven, the sprocket 38 will rotate with the screw, and in either event will transmit the end thrust load through the bearing 42.

The backing plate 32 is substantially circular in its upper portion and of a slightly greater diameter than the diameter of sprocket 38. This configuration is provided in order to protect the sprocket and associated equipment against damage by an inadvertent blow. The plate 32, as previously indicated, extends to the apex 34, and in the apex area has an opening 44 to receive and support a stub shaft 46.'Stub shaft 46 has a small size sprocket 48 non-rotatably secured thereon by means of a pin 50. A chain 51 engages and connects the two sprockets in drive relationship.

In order to support the stub shaft 46 against failure by reason of twisting forces, an auxiliary plate 52 is secured on the opposite end of the tubular body 26 from the plate 32, and extends down to a parallel position with respect to the apex area 34. The plate 42 has an opening 54 to receive the end of the shaft in a close supporting fit. A retainer end cap 56 is secured on the end of shaft 46 to hold the shaft against movement in one direction, and the sprocket 48 will hold the shaft against moving in the opposite direction.

A scissors jack is usually driven by an extension crank handle which is preferably a separate tool which is engaged to the screw 20 by means of an adaptor, much like a socket or a nut.

A connector, which may be considered to be an adaptor, indicated by reference character 58, is secured non-rotatively on the tip end of the screw 20- and is configured J. to receive a drive tool or handle device (not shown) to impart rotative force to the adaptor,-and hence to the screw. Generally, a folding handle having a socket portion on the end is provided with a scissors jack, and the connector or adaptor 58 is formed with an outside hexagonal surface in order to permit longitudinal telescoping of the handle to the adaptor, and then permit rotation drive transmission.

A similar connector adaptor 60 is non-rotatively se cured to the forward end of the lower stub shaft 46. The two adaptors 58 and 60 are substantially parallel and therefore the operator may easily remove the drive handle tool from one adaptor and install it upon the other without delay or difliculty.

This invention, therefore, provides a simplified and convenient construction wherein the two adaptors are substantially evenly spaced, with respect to the position of the operator, in order to avoid any necessity for changing longitudinal positions of the hand tool when changing from one drive adaptor to the other. Furthermore, it is well known that scissors jacks are moved into position by fitting the handle to the adaptor and then thrusting and pulling on the handle. If the handle is engaged with the connector adaptor 60 rather than 58 during such maneuver, the shaft 46 is fully supported to withstand such forces by reason of the spaced dual support provided by the backing plate 32 and the auxiliary plate 52.

Of considerable advantage over: the prior art is the fact that the ratio between the sprocket 38 and the sprocket 48 is large andmay be selected to any ratio desired. The large sprocket is protected by the matching size and configuration of the backing plate 32, and if desired, a cover enclosure may be used to provide further protection. This cover would be secured to plate 32 and wouldcover sprockets 38 and 48 and chain 51 for protection against dirt or damage from other sources, for example.

In use, the connector adaptor 58 is first employed to give a fast direct rotation of the screw in order to lift the pad 18 into engagement with the object being raised. Then the operator will switch to the connector adaptor 60 in order to obtain a mechanical advantage after the resistance begins to slow the operation.

It is well known that a scissors jack is most inefficient at the beginning of the lifting operation, at the very time when the greatest lifting force is needed. Using thegear reduction provided through operation of the connector adaptor 60 overcomes this disadvantage and enables the operator to employ considerable mechanical advantage.

This advantage is particularly desirable for women. Furthermore, it is substantially essential if a heavier vehicle, such as a truck, is being elevated.

The sprocket drive assembly of this invention provides a still further advantage of considerable value. It is well known that scissors jacks are often employed under emergency conditions which subject the user to more or less of an emotional strain. Therefore, avoidance of small disadvantages and annoyances is a great advantage. In those prior art devices requiring opposite directions of drive handle rotation, the human factor will usually cause the operator to turn the drive adaptor in the wrong direction. Annoyances are then encountered whenever the jack is momentarily lowered instead of continued in its upward movement as the drive handle is shifted to the lower.

connector adaptor 60.

By the use of a sprocket and chain construction of this invention, both connector adaptors 58 and 60 are driven in the same direction. Thus, the human tendency to follow a given pattern will usually cause the operator to continue the same direction of handle rotation when driving either of the connector adaptors.

In addition to the sturdiness of the support of the connector adaptor 60, and the advantage of the same direction of drive in both adaptors, the illustrated embodiment of the invention is inexpensive to construct but exceedingly rugged and serviceable for its intended purpose.

While the instant invention has been shown and described herein in what is conceived to be the most practical and preferred embodiment, it is recognized that departures may be made therefrom within the scope of the invention which is therefore not to be limited to the details disclosed herein but is to be afforded the full scope of the invention as hereinafter claimed.

What is claimed is:

1. A collapsible jack, comprising;

(A) a base;

(B) a work-engaging pad spaced from said base;

(C) upper and lower sets of opposed crossed links pivotally connected to said pad and to said base respectively;

(D) a drive trunnion having (1) a body portion with a through opening;

(E) a draw trunnion having (1) a threaded through opening, and

(2) being spaced from said drive trunnion alongv a common axis; (F) an operating screw (1) lying on said common axis (2) threadably engaged in said draw trunnion and (3) passing freely through said opening in said body of said drive trunnion; (G) opposite adjoining ends of said sets of crossed links having pivotal interconnection to said draw trunnion and body portion of said drive trunnion respectively; (H) a first plate (1) mounted on said body portion of said drive trunnion outside the point. of pivotal connection of said links thereto; (I) a second plate (1) mounted on said body portion of said drive trunnion between said opposed links in parallel spaced relationship with said first plate; (J) a first sprocket and drive connector (1) secured to said screw at a point outside said first plate;

(K) a second sprocket and drive connector (1) rotatably carried by said first and second plates,

(2) with said second sprocket lying in a plane common withsaid first sprocket; and

(L) a sprocket chain in drive-transmitting engagement with said first and second sprockets.

2. A jack of the character described in claim 1 wherein said first sprocket has a diameter greater than the space between said sets of crossed links between said trunnions and is larger than said second sprocket.

FOREIGN PATENTS 302,091 10/1932 Italy.

OTHELL M. SIMPSON, Primary Examiner. 

1. A COLLAPSIBLE JACK, COMPRISING; (A) A BASE; (B) A WORK-ENGAGING PAD SPACE FROM SAID BASE; (C) UPPER AND LOWER SETS OF OPPOSED CROSSED LINKS PIVOTALLY CONNECTED TO SAID PAD AND TO SAID BASE RESPECTIVELY; (D) A DRIVE TRUNNION HAVING (1) A BODY PORTION WITH A THROUGH OPENING; (E) A DRAW TRUNNION HAVING (1) A THREADED THROUGH OPENING, AND (2) BEING SPACED FROM SAID DRIVE TRUNNION ALONG A COMMON AXIS; (F) AN OPERATING SCREW (1) LYING ON SAID COMMON AXIS (2) THREADABLY ENGAGED IN SAID DRAW TRUNNION AND (3) PASSING FREELY THROUGH SAID OPENING IN SAID BODY OF SAID DRIVE TRUNNION; (G) OPPOSITE ADJOINING ENDS OF SAID SETS OF CROSSED LINKS HAVING PIVOTAL INTERCONNECTION TO SAID DRAWN TRUNNION AND BODY PORTION OF SAID DRIVE TRUNNION RESPECTIVELY; (H) A FIRST PLATE (1) MOUNTED ON SAID BODY PORTION OF SAID DRIVE TRUNION OUTSIDE THE POINT OF PIVOTAL CONNECTION OF SAID LINKS THERETO; (I) A SECOND PLATE (1) MOUNTED ON SAID BODY PORTION OF SAID DRIVE TRUNNION BETWEEN SAID OPPOSED LINKS IN PARALLEL SPACED RELATIONSHIP WITH SAID FIRST PLATE; (J) A FIRST SPROCKET AND DRIVE CONNECTOR (1) SECURED TO SAID SCREW AT A POINT OUTSIDE SAID FIRST PLATE; (K) A SECOND SPROCKET AND DRIVE CONNECTOR (1) ROTATABLY CARRIED BY SAID FIRST AND SECOND PLATES, (2) WITH SAID SECOND SPROCKET LYING IN A PLANE COMMON WITH SAID FIRST SPROCKET; AND (L) A SPROCKET CHAIN IN DRIVE-TRANSMITTING ENGAGEMENT WITH SAID FIRST AND SECOND SPROCKETS. 